1. Field of the Invention
The present invention relates to evaluation processing for evaluating the image quality of printed matter of an image forming apparatus.
2. Description of the Related Art
As one item for evaluating the image quality of printed matter, an evaluation scheme of homogeneity in page image associated with color reproductivity has been proposed. The evaluation scheme of homogeneity in page image evaluates color and density heterogeneities in one page image (to be referred to as heterogeneity in page image hereinafter, in other words, color differences in page image) using a small color difference spectrometer and XY stage. Therefore, an image based on image data of an identical density is formed on the entire page, the reflection characteristic value of the formed image is measured, and statistical values such as a maximum value, average value, standard deviation, and the like are acquired. Whether or not the heterogeneity in page image falls within a permissible range is determined using the statistical values of the measured data, i.e., the values such as the maximum value, average value, standard deviation, and the like.
However, when one observes the homogeneity in page image with his or her own eye, the permissible level associated with color reproduction with respect to an identical color signal changes depending on the distance from an interest point. That is, there are visual perception characteristics in that one easily senses a color difference if the distance from the interest point is short, but one hardly senses the color difference with increasing distance. Since the above evaluation method of homogeneity in page image does not consider such human visual perception characteristics, the correlation between the actually finished image and the evaluation result cannot be exploited fully.